Melissa Sheer got her first au pair two years ago to help care for her two daughters. At first, the Spanish babysitter she’d found through an agency that helped match families with young live-in help, seemed like a great fit.

But then the au pair started staying out late and became demanding about the family car. It turned out that her boyfriend had followed her to the US and was living nearby — eating groceries purchased with Sheer’s money and accompanying the au pair when she was with the children.

“My then-7-year-old and her friend told us,” said Sheer, 40, who lives in New Jersey. “Within a few days she was on a plane back to Barcelona.”

Hiring live-in help is tricky business, whether it is a nanny who minds the children and looks after their schedule and laundry, an au pair who does basic childcare and child-related household chores, or a full-fledged house manager. After all, this person will live in your home with you, so finding the right fit is important.

Then there are the financial logistics that come with having a household employee, including taxes and insurance. None of this is cheap, but the ability to have a tidy house, a hot meal on the table and relaxed children can make it all worthwhile.

In the US, an au pair costs about $200 a week (not including program fees of about $7,000 per year and a small stipend for education), and a nanny can cost between $400 and $1,200 per week, depending on location and how many hours she works. In the UK, an au pair is at least £80 ($134) per week and a live-in nanny may be as much as £380 ($637) per week, according to BabyCentre.co.uk.

Foreigners living in Indonesia commonly have an employee called a Jaga living on grounds who provides security and yard maintenance, costing up to 2.4m rupiah ($500) per month, according to Katie Erickson, a financial planner who lives in Jakarta. She also has a part-time maid and a full-time driver who live nearby—because household help is part of everyday life in Indonesia and because traffic is “notoriously terrible,” Erickson said.

“Having personal staff is extremely relevant to my life here, and I’m still adjusting to this,” Erickson said. “Our help has become like an extended family, but I struggle between the guilt over not doing things myself, and the management it requires to have everything coordinate smoothly.”

While you probably aren’t going to hire your own full-time driver (unless you live in Jakarta), a live-in nanny or au pair may be something you’re considering. Here’s how to keep the household peace — and budget:

What it will take: You will need time to find a placement agency and research the right fit for your family, you’ll need enough money for the extra costs and you’ll also need the proper space in your home for an extra person. Some sites to consider: aupairinamerica.com, aupair.com, enannysource.com, and nanniesinc.com.

How long you need to prepare: Depending on where you live and where your hired help hails from, you may need as little as a week or as long as a year. Those coming from another country may need weeks or months to acquire a visa and make travel arrangements. Most organised au pair programs say it takes 4 to 6 weeks to secure a visa and travel arrangements. You may also need time to prepare your home for your employee.

Do it now: Figure out what you want. “The biggest mistake employers make in hiring staff is jumping straight into the hiring process without knowing what they actually want,” said John Robertson, consultant to the UK’s ButlerForYou.com, a household staffing agency.

“The first step is to articulate your home ‘mission statement’ as any company would do, and then to determine a comprehensive list of responsibilities,” he said. In other words, what do you want your employee to do, and when and how do you want her to be doing it?

Consider all the costs. It’s not just about weekly fees. “Can you afford… any associated renovations, or purchases of things like furniture?” said Julia Chung, a financial and estate planner with Facet Advisors in Langley, British Columbia in Canada.

Among other costly considerations: will you need to provide health insurance? Will you buy a vehicle for her or add her to your auto insurance? Are there pension plan requirements in your country? In Canada, for instance, pension contributions are mandatory for employers and employees, so you’ll have to allocate an extra 4.5% to that. Worker’s compensation and unemployment insurance will also cost extra. In the US, worker’s compensation might be 2% to 4% of an employee’s annual salary.

Make space. A domestic employee will need a private bedroom, preferably not on the same floor as the adults in the household. She will also need access to her own bathroom, or one she might share with the children — but not with other adults.

“Lots of times families will finish what they call a ‘nanny suite,’” said Kathleen Webb, co-founder of HomeWork Solutions, a US payroll and tax service company for families that employ household workers. “They’ll finish the attic over the garage or the area in the basement. Having the right physical layout to make this work is really key; having the ability to close doors and be separate from each other.”

Do it later: Respect your employee’s time. When someone lives in your house, there’s the temptation to feel like she’s always available for you. But constantly asking a nanny to watch the children while you “run out” during her off hours can make her feel like she’s working all the time. And if you’re supposed to be home at 6 and you arrive at 6:45, plan to pay for the extra time.

Get help with payroll if needed. Having a household employee often comes with red tape — taxes, worker’s compensation and unemployment insurance are just a few examples. Determining what’s required can be a headache, and doing it incorrectly can result in fines and late fees. If you are too overwhelmed to handle the task, hire a service to do it for you. “Somewhere between 15% and 20% of families get some sort of external help with this,” Webb said. That kind of service might cost $500 to $800 a year.

Do it smarter: Call references yourself. An agency will typically do a thorough background check and provide written references, but you may want to call a candidate’s former employers yourself rather than letting the agency do it. That way you can see whether previous families were looking for the same things you are. Another family may have loved someone who’s the absolute wrong fit for you.

“Every family situation is unique and different,” said Steven Laitmon, founder of the Calendar Group, a US domestic staffing and consulting agency. “I always encourage them to reach out.”